v1.4.0 - independent test re-run

Enforcement

• /build re-runs the test suite itself against each task branch and gates on its own result, rather than trusting the Worker's pasted test output (now only cross-checked for fabrication).
• CONTEXT.md requires a Test command: field. /build stops at startup without it; /triage won't mark a task agent-ready without it.

Wording

• "seam" -> "test point" and review "axes" -> "tracks" across all commands and docs.